1. Field of the Invention
The present invention relates to a spell verification electronic typewriter which utilizes a spelling dictionary to verify whether a word is spelled correctly.
2. Description of the Related Art
Conventional electronic typewriters with spell verification include a first microprocessor to control typewriter functions such as keyboard input and printer output, and a second microprocessor to control the spell verification function. Thus, as shown in U.S. Pat. No. 4,689,768, a printer processor accepts keyboard input and causes a printing element to print characters that correspond to the input. In response to a request to verify spelling, a spelling verification processor, which is independent of the printer processor and includes its own program and data storage memory, is actuated to determine if the keyed-in word is correctly spelled.
It has been considered to combine typewriter functions and spell verification functions into one processor. However, because of the nature and complexity of those functions, it has heretofore been necessary to provide the processor with computer-like structure such as external memories and address and data buses. For example, to control the keyboard and the printer and at the same time provide for access to a spelling dictionary, the processor must ordinarily include an address bus and a data bus to send and receive information to and from the printer and the keyboard, to send and receive information from the spelling dictionary, and to send and receive processor instructions and print data from external program memory and data memory. Moreover, simply to coordinate this computer-like structure and ensure its functionality, the processor must execute extra functions, instructions that are unrelated to electronic typewriter or spell verification functions, such as bus contention functions, device-busy checking, read/write coordination, etc.
Such computer-like structure increases the cost and complexity of the electronic typewriter, as well as requiring high development costs. These costs recur for each different model of electronic typewriter.